Abstract
ABSTRACTIn diblock copolymers, the constraining effects of different stereochemical structure of high‐Tm block on crystallization and melting behaviors of other constituent are supposed to be different. In this work, PEG‐b‐PDLLA and PEG‐b‐PLLA were synthesized, and crystallization kinetics, crystalline structure, melting behaviors of PEG blocks and morphology development in these systems were evaluated. Compared to those connected to PLLA, PEG‐b‐PDLLA exhibited lower crystallization rates, implying that connectivity of amorphous chain exerted more pronounced effect on crystallization rate of PEG than that of steric hindrance of PLLA crystallites. While all PEG‐b‐PDLLA samples showed a single endothermic peak during heating process, multiple melting peaks were observed in PEG‐b‐PLLA associated with composition, crystallization temperature and cooling rate of PLLA. A lamellar structure was formed by the crystallization of PEG in all PEG‐b‐PDLLA, however, when PEG‐b‐PLLA crystallized at room temperature directly, unexpected results occurred: lamellar for diblock copolymers with 31.5 and 48.0 wt% PLA or cylindrical structure for the diblock copolymers with 56.1 and 63.8 wt% PLA. Depending on composition, PEG‐b‐PLLA created one or two types of lamellar stacks after sequential crystallization of PLLA and PEG. © 2020 Wiley Periodicals, Inc. J. Polym. Sci. 2020, 58, 455–465
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